using Stream = System.IO.Stream;

namespace Spring.Expressions.Parser.antlr;
/*ANTLR Translator Generator
 * Project led by Terence Parr at http://www.jGuru.com
 * Software rights: http://www.antlr.org/license.html
 *
 * $Id:$
 */

//
// ANTLR C# Code Generator by Micheal Jordan
//                            Kunle Odutola       : kunle UNDERSCORE odutola AT hotmail DOT com
//                            Anthony Oguntimehin
//
// With many thanks to Eric V. Smith from the ANTLR list.
//
/*A Stream of characters fed to the lexer from a InputStream that can
 * be rewound via mark()/rewind() methods.
 * <p>
 * A dynamic array is used to buffer up all the input characters.  Normally,
 * "k" characters are stored in the buffer.  More characters may be stored during
 * guess mode (testing syntactic predicate), or when LT(i>k) is referenced.
 * Consumption of characters is deferred.  In other words, reading the next
 * character is not done by conume(), but deferred until needed by LA or LT.
 * <p>
 */

// SAS: added this class to handle Binary input w/ FileInputStream

public class ByteBuffer : InputBuffer
{
    // char source
    [NonSerialized()] internal Stream input;

    private const int BUF_SIZE = 16;

    /// <summary>
    /// Small buffer used to avoid reading individual chars
    /// </summary>
    private byte[] buf = new byte[BUF_SIZE];

    /*Create a character buffer */
    public ByteBuffer(Stream input_) : base()
    {
        input = input_;
    }

    /*Ensure that the character buffer is sufficiently full */
    override public void fill(int amount)
    {
//			try
//			{
        syncConsume();
        // Fill the buffer sufficiently to hold needed characters
        int bytesToRead = (amount + markerOffset) - queue.Count;
        int c;

        while (bytesToRead > 0)
        {
            // Read a few characters
            c = input.Read(buf, 0, BUF_SIZE);
            for (int i = 0; i < c; i++)
            {
                // Append the next character
                queue.Add(unchecked((char) buf[i]));
            }

            if (c < BUF_SIZE)
            {
                while ((bytesToRead-- > 0) && (queue.Count < BUF_SIZE))
                {
                    queue.Add(CharScanner.EOF_CHAR);
                }

                break;
            }

            bytesToRead -= c;
        }
        //			}
//			catch (IOException io)
//			{
//				throw new CharStreamIOException(io);
//			}
    }
}
